Time to change banks/credit card account carriers.
We have yet to visit a country where the best exchange rate was NOT at an ATM.
We also find that it always pays to use the local currency. As of Friday, the US dollar was 12.5 pesos. Your bus ride would have been a lot cheaper if you had used pesos.
We all live and learn.
Last November the big change was that Bank of America kept their free use of Santander ATM's, but initiated a 3% foreign transaction fee on every withdrawal. That adds up fast. That's when we gave up a 50+ year relationship with BofA and went to CapOne for everything. We had already switched from the 2.5% fee minimum for foreign use of credit cards with BofA and gone to CapOne's free international cards. It was a total pain in the butt to do, but worth it in the end.